In recent years, in systems that perform noncontact communication such as RFID systems and near field communication systems that are increasingly being used, in order to perform communication between portable electronic apparatuses, such as cellular phones, or between a portable electronic apparatus and a reader/writer, a communication antenna is installed in these apparatuses.
When such a noncontact communication antenna is installed at a back side of a metallic member, a magnetic field is intercepted by the metallic member. Therefore, it is not possible to perform communication with, for example, a reader/writer that is disposed on a side of the metallic member that is opposite to a side where the antenna is disposed.
An antenna device in which an antenna coil is disposed at a back side of a metallic member and a conductor opening is provided in the metallic member is disclosed in Japanese Patent No. 4687832.
FIG. 19(A) is a back view of an electronic apparatus including the antenna device in Japanese Patent No. 4687832. A back side of the electronic apparatus is the side that is caused to face a reader/writer antenna with which communication is performed. FIG. 19(B) is a plan view of an inner side of a lower-portion housing at the back side.
As shown in FIG. 19(A), a conductor layer 22 is formed at an outer surface of the lower-portion housing 1. The conductor layer 22 is, for example, a metalized film of aluminum or the like. An opening CA is formed in the conductor layer 22. In addition, a slit SL is formed consecutively between the opening CA and an outer edge. As shown in FIG. 19(B), an antenna coil module 3 is disposed at an inner surface of the lower-portion housing 1 so as to partly overlap the opening CA.
As another example, Japanese Patent No. 4626413 discloses a structure in which an antenna coil is disposed at an end portion of a communication terminal and communication is possible from both the front and back of the communication terminal.